The present invention relates to a discharge device employed in a vehicle that includes an electric circuit having capacitors, and forcibly stops electricity supply to the electric circuit when an abnormality related to a collision is detected. More specifically, the present invention relates to a discharge device that forcibly discharges capacitors, in addition to stopping the electricity supply, when an abnormality is detected.
In recent years, vehicles such as hybrid vehicles, electric vehicles, and fuel cell vehicles have been equipped with in addition to motors and a storage battery, which function as power source, an electric circuit for driving the motors with electricity from the storage battery. The electric circuit includes a converter and inverters. The converter raises the voltage of the electricity supplied from the storage battery, and outputs the electricity to the inverter. The inverters convert the received direct-current electricity to an alternating-current, which is suitable for driving motors, and delivers the electricity to the motors.
In such vehicles, when an abnormality such as a collision is detected, the connection between the storage battery and the electric circuit is interrupted to forcibly stop the electricity supply to the electric circuit, thereby eliminating adverse effects caused by high voltage. Also, in a vehicle equipped with an electric circuit having capacitors, the capacitors may be forcibly discharged, in addition to stoppage of the electricity supply.
For example, Japanese Laid-Open Patent Publication No. 2006-141158 discloses a vehicle control device that, when a vehicle collision is detected, zero torque control is executed to quickly discharge capacitors during traveling of the vehicle. The zero torque control refers to control in which a motor driving circuit is operated without generating torque from the rotary shaft of the motor-generator. To execute the zero torque control, the charge (electricity) stored in either the capacitors of the inverters or the capacitor of the converter is used.
Before execution of the zero torque control, the automatic transmission is switched to the parking lock state. Accordingly, this is to prevent torque from being transmitted to the drive wheels in the unlikely event that the motor-generator generates torque during the zero torque control.
However, in the vehicle control device of the above publication, the zero torque control is executed to discharge the capacitors only on condition that the converter and the inverters are functioning normally. If the converter and the inverters are not functioning normally, the zero torque control cannot be executed properly. As a result, the capacitors cannot be properly discharged. That is, whether or not the capacitors can be properly discharged is greatly influenced by the state of the converter and the inverters.
Particularly, at the time of detection of a collision, at which discharge is performed, the converter and the inverters are likely to receive an impact. This is likely to hinder proper execution of the zero torque control.
An additional discharging mechanism may be provided to discharge the capacitors. However, if such a discharge mechanism is provided at a position located away from the case accommodating the electric circuit, the wires connecting the discharge mechanism to the electric circuit are likely to be broken by the impact.